254 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1941 



Food sources. — No consistent effort has been made to determine 

 the nicotinic acid content of foods accurately. Most of the studies 

 along this line have been concerned with determination of pellagra- 

 preventing value directly. Some of these studies have been made 

 with dogs as subjects and some with human beings. It is difficult to 

 correlate the two kinds of data. Appraisal of pellagra-preventing 

 value of foods on the basis of content of nicotinic acid depends upon 

 the quantity of this substance required for the cure and prevention 

 of pellagra ; and this has not yet been deJBnitely determined, although 

 it can be stated approximately. 



Milk, lean meats, eggs, fish, liver, and some vegetables have long 

 been known to be valuable in the cure and prevention of pellagra. 

 Among the vegetables, green leaves are especially effective, and the 

 legumes (peas and beans) and tomatoes have some value. 



Losses of nicotinic add. — The pellagra-preventing value of foods 

 is not reduced easily. Foods have been heated in an autoclave or 

 pressure cooker as long as 6 hours without showing a decrease in 

 effectiveness. Canned foods seem to be equally as good as the 

 corresponding fresh ones. 



VITAMIN K (THE ANTIHEMORRHAGIO VITAMIN) 



Properties. — ^Vitamin K is one of the newer vitamins. It is a color- 

 less or slightly yellowish crystalline substance soluble in fats but 

 not in water. It seems to be resistant to heat but is destroyed by 

 alkalies and certain substances that bring about oxidation. 



Food sources. — Vitamin K is fairly widely distributed in foods. 

 It occurs abundantly in green leaves, alfalfa having been one of the 

 chief sources from which concentrates have been prepared. Flowers, 

 roots, and stems of plants contain less than leaves. The vitamin is 

 present in soybean oil and some other vegetable oils and in tomatoes. 

 It is not present in fish-liver oils, but decomposed fish meal has been 

 the source of a substance having vitamin K activity, differing slightly 

 from the vitamin K of alfalfa. A number of compounds are known 

 to have properties ascribed to vitamin K but how many of these occur 

 naturally is not known. 



VITAMIN E 



Properties. — Vitamin-E activity is shown by several substances. 

 The one of most importance from the standpoint of its natural occur- 

 rence is alpha-tocopherol. This has been separated from wheat-germ 

 oil and cottonseed oil as a light yellow viscous oil. 



Food sources. — Vitamin E occurs in many of the various types of 

 foods considered essential in a well-balanced diet and it is not dif- 

 ficult to obtain an adequate supply. Foods known to contain vita- 



